This invention relates to a body motion detector comprising a plurality of sensors each for outputting a signal according to a body motion and serving to carry out a measurement by selecting those of the plurality of sensors which are suited for the measurement.
As an example of body motion detector adapted to select output signals (or sensors) out of a plurality of sensors for carrying out a main measurement, Japanese Patent Publication Tokkai 9-223214 disclosed a pedometer characterized as selecting one of output signals from a plurality of sensors on the basis of a signal outputted from a mechanical angle-detecting sensor such as an optical sensor. Japanese Patent Publication Tokkai 11-42220 disclosed a body motion detector adapted to select one of a plurality of sensors for a main measurement when the directions of its attachment is known. A body motion detector of still another kind to be affixed at a fixed position and in a fixed direction, adapted to measure a body motion by using an acceleration sensor with two or three axes for identifying the form of motion such as walking on a horizontal ground, uphill walking and downhill walking, was disclosed in the Proceedings of the 11th Biophysics and Engineering Symposium BPES 96, pp493-496. An acceleration waveform obtained when a person walks with an acceleration sensor with three axes affixed to the waist was analyzed in this report to distinguish different modes of walking. In this experiment, however, the acceleration detector must be affixed securely so as not to change its orientation.
The method of providing a mechanical detector such as an angle-detecting sensor to select an output signal is disadvantageous not only because of its cost of production but also because the detector becomes larger by the space occupied by the angle-detecting sensor. If the detector must be kept at a certain direction, this will limit the position where the detector can be attached. If the detector is attached in a wrong direction, it is not possible to obtain a correct measured result.
It is therefore an object of this invention, in view of these problems of the prior art technologies, to provide a body motion detector which can be freely attached to or carried by the user and can detect the body motion with high accuracy, independent of the orientation of the detector.
It is another object of this invention to provide such a body motion detector which can be compact and can be produced relatively inexpensively.
A body motion detector according to this invention may be characterized not only as being adapted to be attached to or carried by a user for detecting body motions of the user but also as comprising a plurality of sensors each for detecting body motions of the user in a specified direction to output a body motion signal according to the user""s body motion, each of them being disposed so as to detect the body motion in a different direction, and selecting means for selecting one of these sensors by carrying out calculations on signals outputted from these sensors. The body motion detector thus detects the body motion in a specified direction selectively from output signals from the selected body motion sensor. With a body motion detector thus structured, the user""s body motion can be detected accurately because the detection is made selectively on the basis of the signals outputted from one of the plurality of sensors selected to be more appropriate than the others for the detection. Since the selection is made by a calculational routine, furthermore, there is no need for an extra component such as an angle detector for detecting the orientation of the body motion detector, the detector as a whole can be made compact and at a lower cost.
The invention also provides a body motion detector comprising not only a plurality of sensors as described above but also orientation detecting means for detecting the orientation of the body motion detector itself from signals outputted from these sensors and body motion detecting means for detecting the user""s body motions by carrying out calculations on the signals outputted from these sensors, corresponding to the orientation as detected by the orientation detecting means.